In the revealing interview at his Cornish home, le Carré, whose real name is David Cornwell, described how his experiences working as a spy during the 1950s and 1960s, and his childhood shaped his writing.

The 79-year-old wrote his third novel in just six weeks. He will release his 22nd novel, Our Kind of Traitor, later this week.

His books, including the bestselling The Spy Who Came in from the Cold, and Tinker Tailor Soldier Spy, explore a world of espionage, money-laundering and moral ambiguities.

Le Carré worked for MI5 and MI6 during the 1950s and 1960s, using the cover of a British diplomat in Germany to run agents and lure defectors.

“In was in those days most definitely a calling and for all that I’ve written about it, it was a pretty decent calling, in the sense that we were very patriotic people in ways I don’t think we are anymore.

“The ethic, which I believe has been greatly undermined in recent times, was that we spoke truth to power,” he said.

However his cover was betrayed by the double-agent Kim Philby (pictured), the highest-ranking British intelligence officer who worked as a spy for the Soviet Union.

“I had been betrayed by Philby, I actually refused to meet Philby in Moscow in 1988. For me, Philby was a thoroughly bad lot, just a naturally bent man.

“You have to remember that Philby was in line to become head of SIS. I wouldn’t have trusted him with my cat for the weekend,” he said.

Russian warningsLe Carré’s new book features Russian oligarchs, money laundering and compromised British politicians. In researching his latest book, Mr le Carré said he became concerned about so readily accepting money from Russians.

“I asked a couple of top British bankers this question. ‘I am Mr Orlov, I have $100m to invest in your bank.’

I love interrogation, I find that really fascinating. I did quite a lot of interrogation and it was always of the long patience discussions, the befriending and so on.

“The banker’s answer is ‘well we’re not detectives’. Basically what they were saying is show me your passport and a utilities bill and we’ll open an account for you.

“So there is the constant mystery, which I think is exemplified in the present situation – What is black money? Then does it go grey, and when does it go white?”

“I think at the financial level, we’d go practically anywhere for money. I think there’s probably a big competition in the world, first for Russian oil and secondly for Russian money. Nobody much cares that most of the big fortunes of Russian money are actually stolen in one way or another. They were stolen when the state silver was stolen.

“It seems that we’ve grown closer to Russia in what a disagreeable country Russia is becoming.”

Le Carré also raises concerns about the politicians in the UK who he believes have become too close to the Russian oligarchs.

“What I am concerned about is the amount of influence they can exert also in both houses of Parliament and I did pick up rumours from the intelligence community and ex spooks as I was writing the book that there is a great deal of hidden influence – particularly in the upper house.”

During the wide-ranging interview, le Carré explains how the lead character of many of his books, George Smiley, foreshadowed the excesses of the modern capitalist world.

“Funnily enough, in the last address that George Smiley made to the world, in a little book I wrote to finish Smiley to off, he said: ‘Now we’ve dealt with communism, our next job is to deal with the excesses of capitalism’. I believe that’s true,” he said.

The long journey to meet John le Carré

The night sleeper drew exhaustedly into Penzance station, I checked my bag, and made my way onto the platform, writes Jon Snow.

A cascade of other bleary eyed passengers were tumbling out of the train. As I made my way through the thicket of people, I glimpsed the shock of white hair, the weather-beaten face and the upright patrician form of the man I had come to meet.

He seemed to spot me as I spotted him - striding towards me at the same pace that I was closing in on him. A warm handshake and we were heading for his small car and the journey to our cliff top assignation.

John le Carré is merely his writing cover, David Cornwell being his real-life name. He has lived astride these spectacular Cornish cliffs for forty years. And in those forty years has never seen fit to pave the gravel track to his home. One sense the mile long hedged strip is part of the fortification that guards his writing solitude.Read more

The startThe writer described his first novel, the best-selling The Spy Who Came in from the Cold, as a book that expressed his own personal history “more than any other” – and one he has still to better.

“I wanted, I thought, to get out of the secret world completely. I was working in the British embassy in Bonn, and in five or six weeks wrote it. I was getting up at four or five in the morning, driving my family mad.”

“That was the book that not only altered my life, but probably expressed feelings more directly, at the right moment in history, my personal history and history of the outside more than any other,” he said.

“Most writers who become successful can actually talk to one particular benchmark book.

“If we think Kingsley Amis, we think Lucky Jim. It doesn’t matter how much he wrote before or since. If we think Daphne du Maurier, we think Rebecca.

“Popular writers have usually got one flag they can always wave. And it haunts them, it haunts me. Can I ever write another Spy Who Came in from the Cold? The answer is no I can’t. But I can do other stuff.”

Le Carré has also been an outspoken opponent against the war in Iraq, publishing an essay in 2003 called The United States has gone mad.

He also expressed concern about the methods modern-day intelligence agencies have been accused of using to gain information.

“I love interrogation, I find that really fascinating. I did quite a lot of interrogation and it was always of the long patience discussions, the befriending and so on.

“I have complete contempt for the other sort of interrogation.

“Most people, if they want to confess something, they need help. They need compassion. They need a pastoral connection and an intelligent connection, not a bullying one.”

For Le Carré, the writing life is “the only life”.

“It’s all I know now. It’s that and my family. We have very little social life.”

“I can populate these hills when I go for walks with the characters of my imagination. It’s reconnection with childhood.”

“I don’t make plots in advance. I don’t make great march routes I actually try to throw people into a messy life and see how they’ll sort it out while I’m writing. So the whole adventure is one I share with the reader.”